1. Technical Field
The present invention relates to a method for taking up play in a drive line when a change in load occurs in a drive system in a motor vehicle. The invention also relates to an arrangement for implementing the method.
2. Background Information
In modern motor vehicles, vibrations can sometimes occur in the drive line. In this context, drive line means all the component parts of the transmission between the output crankshaft of the engine and the driving wheel axles. Vibrations may arise, for example, if there is play in the drive line when torque is applied to the latter from the engine. This play can also occur during engine braking, when a negative torque loads the drive line and winds the latter up like a torsion spring. When the throttle is opened, the drive line is subjected to a positive torque, which means that it is subjected to a change in load. This change in load, when the torque applied to the drive line changes from braking to driving, can bring about a jerk with subsequent vibrations throughout the drive system. The main cause of this jerk is an unchecked acceleration of the flywheel when the drive line passes through play in the line.
Apart from being an unpleasant sensation for the driver and passengers, these vibrations can give rise to unnecessary wear on the drive line. Under certain circumstances, for example, on curves or on slippery surfaces, variations in the torque delivered to the driving wheels can cause dangerous traffic situations.
Referring to International Patent No. WO 97/08440, for example, a drive system arrangement including an electrical machine and a method for implementing the electrical machine in the drive system is taught. The electric motor is coupled to the drive line for regulating torque fluctuations. By measuring the torque on the drive line and feeding these measured values back to a control system, the electric motor can be continuously regulated so as to counteract jerks and vibrations associated with changes in load. The disadvantage of this system is that it is relatively complicated and requires a control system capable of reacting to rapid variations that can occur in the drive line. If vibrations arise for which the control system is not programmed, there may be problems in damping these quickly enough. The system is moreover intended for counteracting vibrations in the drive line as a function of measured torque variations; that is to say, the system reacts only when a jerk has started to occur and/or when the vibrations can be measured.
Other known solutions include holding back the internal combustion engine so that the change in torque of the engine is zero when the drive line passes through the play. This can be accomplished by damping the movement of the throttle (for an electric throttle), resulting in inferior response, or by reducing the ignition and/or regulating the air and/or fuel supply, resulting in higher fuel consumption in addition to inferior response.